Multi-optical fiber (MF) connector modules are used to mechanically couple the ends of a plurality of optical fibers to a parallel optical communications module that has a plurality of optical channels. The parallel optical communications module may be a parallel optical transceiver module having both transmit and receive optical channels, a parallel optical transmitter module having only transmit optical channels, or a parallel optical receiver module having only receive optical channels. A typical MF connector module includes an optics system that couples light between the ends of the optical fibers held in the MF connector module and the parallel optical communications module. Within the parallel optical communications module, an optics system couples light between the MF connector module and a plurality of optoelectronic devices disposed inside of the parallel optical communications module. For transmit optical channels, the optoelectronic devices are electrical-to-optical converters such as laser diodes or light-emitting diodes (LEDs). For receive optical channels, the optoelectronic devices are optical-to-electrical converters such as P-intrinsic-N (PIN) photodiodes.
The MF connector modules and the parallel optical communications modules typically have mating features on them that allow them to be fixedly or removably mechanically coupled (i.e., mated) with one another. A variety of MF connector modules and parallel optical communications modules exist in the market today that are designed to mate with one another in a way that optically aligns the optical pathways between the ends of the optical fibers and the respective optoelectronic devices to enable optical data signals to be efficiently optically coupled between ends of the optical fibers and the respective optoelectronic devices. In designing and manufacturing the MF connector modules and the corresponding parallel optical communications modules, great care is taken to ensure that once the modules are mated together, very precise optical alignment exists along the optical pathways.
Inside of the MF connector module, the ends of the optical fibers are typically held in alignment with respective lenses of the optics system of the MF connector module. The lenses of the connector module couple light between the ends of the optical fibers and the optics system of the parallel optical communications module, which often folds the optical pathways by some angle (e.g., 90°). However, the folding of the optical pathways is sometimes performed by the optics system of the MF connector module, or folding may be performed by each of the optics systems.
The alignment of the optical pathways that extend between the ends of the optical fibers, the optics system of the MF connector module, the optics system of the parallel optical communications module, and the optoelectronic devices of the parallel optical communications module should be very precise in order to ensure good optical coupling efficiency and good performance. A variety of configurations exist for holding the ends of the fibers in fixed, aligned positions within the MF connector module. It is well known to use a V-groove configuration in the MF connector module for holding the ends of the optical fibers in fixed, aligned positions within the MF connector module. The ends of the optical fibers are positioned in respective V-grooves and then a refractive index matching epoxy is used to fix the ends in position within the respective V-grooves. A cover is sometimes placed over the V-grooves to protect the fiber ends and to help hold them in position.
One potential problem with such V-groove configurations is that the V-grooves do not always perfectly align the ends of the respective fibers with the lenses of the MF module. This is because the optical fibers do not always conform to the V-grooves. The optical fibers tend to act like rigid rods in the V-grooves in that misalignment of the fiber at the back of the V-groove will result in misalignment of the fiber at the front of the V-groove. For example, if the fiber has ridden up the edge of the respective V-groove at the back of the V-groove, it will usually also ride up the edge of the V-groove in the front of the V-groove. In addition, optical fibers of an optical fiber ribbon cable are not always parallel to one another in all planes once the fibers have been freed from the cable and stripped of their jackets. Fibers in a ribbon cable have a “set,” which means that when freed from the cable and stripped of their jackets, they curl in multiple directions and are not all parallel in all planes. The fiber “set” makes it difficult to achieve the needed micron-level alignment accuracy of the fiber ends with their respective lenses.
Moreover, if the V-grooves are formed in plastic, the V-grooves may deform in the areas where a load is applied when the fibers are pressed into them. This can cause the front portion of the fiber end (end portion nearest to the lenses) to lift upwards away from the V-groove, even if the deformation is within the elastic stress range of the plastic. This upward lifting of the fiber end in combination with the “set” problem can mean that a different force is acting on each fiber due to its unique set, which can cause the V-grooves to deform by unique amounts for each fiber. This, in turn, can result in a unique alignment error for each fiber.
A need exists for an MF connector module and methods that enable ends of optical fibers to be installed and held in an MF connector module in precise alignment with respective optical axes of the module.